ceph/src/boost/libs/hana/example/fold_right.cpp

   1 // Copyright Louis Dionne 2013-2017
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #include <boost/hana/assert.hpp>
   6 #include <boost/hana/fold_right.hpp>
   7 #include <boost/hana/tuple.hpp>
   8
   9 #include <sstream>
  10 #include <string>
  11 namespace hana = boost::hana;
  12
  13
  14 auto to_string = [](auto x) {
  15     std::ostringstream ss;
  16     ss << x;
  17     return ss.str();
  18 };
  19
  20 int main() {
  21     auto f = [=](auto element, std::string s) {
  22         return "f(" + to_string(element) + ", " + s + ")";
  23     };
  24
  25     // with an initial state
  26     BOOST_HANA_RUNTIME_CHECK(
  27         hana::fold_right(hana::make_tuple(1, '2', 3.0, 4), "5", f)
  28             ==
  29         "f(1, f(2, f(3, f(4, 5))))"
  30     );
  31
  32     // without initial state
  33     BOOST_HANA_RUNTIME_CHECK(
  34         hana::fold_right(hana::make_tuple(1, '2', 3.0, 4, "5"), f)
  35             ==
  36         "f(1, f(2, f(3, f(4, 5))))"
  37     );
  38 }